King Fahd University of Petroleum & Minerals

Department of Mechanical Engineering

Machine Design - II Laboratory - ME 308 - Term 991

Project 3


  1. Calculate the Nominal Velocity Ratio (VR):
  2. VR = np/average ng

  3. Specify a reasonable Module (m):
  4. m = 4                                                                                (mm)

  5. Select the number of teeth on the pinion (Np):
  6. Hint:

    Minimum number of teeth to avoid interference for pinions having 20 pressure angles is 18

    Select Np= 28

  7. Calculate the Pinion Diameter (dp):
  8. dp = Np m                                                                         (mm)

  9. Calculate the number of teeth on the gear (Ng):
  10. Ng = Np VR

    Round-off the calculated value to a closest higher integer value

  11. Calculate the Gear Diameter (dg):
  12. dg = Ng m                                                                         (mm)

  13. Calculate & Check the final Output Speed (ng):
  14. ng = np (Np/Ng)                                                                  (rpm)

    Check if this value falls within the specified output speed range, i.e. (270~280 rpm)

  15. Calculate the Center Distance (C):
  16. C = (Np+Ng)m/2                                                                   (mm)

  17. Calculate the Pitch Line Velocity (n t):
  18. n t = p dpnp/60000                                                                (m/sec.)

  19. Calculate the Tangential Force (Wt):
  20. Wt = P 1000/n t                                                                (N)

  21. Calculate the Face Width (F) of the gears:
  22. F = (8~16)m                                                                         (mm)

  23. Calculate Bending Stress on the pinion (s tp) and gear (s tg):
  24.                                                 (MPa)

  25. Calculate the Contact Stress (s c) on the gear pair:
  26.                                           (MPa)


  27. Select Materials for the pinion and gear depending upon the hardness values for each stress



Brinell Hardness

Selection Procedure

Bending Stress on Pinion


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Contact Stress on Gear Pair


Bending Stress on Gear